Protein-protein interactions involving specific DNA binding domains appear to play a critical role in gene transcription and its regulation. Our working hypothesis is that such regulatory mechanisms exist in both Sertoli cells and meiotic germ cells and mediate transcriptional activation of elements (e.g. STAT-GAS DNA binding complexes) in the promoters of cytokine-responsive genes, thereby influencing critical transitions in phenotypic expression. Our workplan will use both loss- and gain- of function experimental models to address the roles of STAT-4, STAT-6 and the tyrosine kinase JAK3 in meiotic and early haploid gene expression. Using meiotic prophase as a focal point, we will examine whether critical transition points are influenced by the activation and/or inhibition of spermatocyte STAT-DNA binding. In the pre- meiotic, meiotic prophase and early haploid germ cells, we propose to test whether the transcription factors STAT-4 and STAT-6 will define (a) the platform characteristics of the DNA binding complexes formed following a cytokine signal, (b) the potential for transcriptional control of those opioid (e.g. germ cell specific enkephalin promoter) and meiotic genes (e.g. synaptonemal complex) whose promoters contain functional and distinctive STAT-binding elements and, (c) molecular mechanism(s) mediating the paracrine interactions between germ cells and Sertoli cells (e.g. somatic cell enkephalin promoter and opioid receptors) in a stage-specific manner. Studies proposed in Specific Aims 1 and 3 will test the hypothesis that interleukin-12, interleukin-4, and interferon- alpha/gamma represent both positive and negative autocrine/paracrine cues that influence meiotic gene expression and progression to the early haploid phenotype. Those studies planned in Specific Aim 2 will characterize the Sertoli cell- specific mechanisms that mediate the paracrine interactions subserved by interleukin and opioid growth factors. We anticipate that the results of our studies will identify and further characterize novel transcription factors involved in the regulation of meiosis in the male germ line. The testis represents a unique system in which to delineate the consequences of JAK3 tyrosine phosphorylation, cell-to-cell signalling via interleukin-4 and interleukin-12 during development, and the distinct roles of STAT-4 and STAT-6 in gene transcription, providing mechanistic insight that ma also be relevant to lymphocyte development and immune disorders.